1. Field of Invention The invention relates generally to polymerized benzotriazole compounds as ultraviolet (UV) light stabilizers and absorbers, and the incorporation of these compounds into various plastics. Preferred compounds are 2(2-hydroxynaphthyl) 2H-benzotriazoles. These naphthyl-based benzotriazole compounds are polymerized to provide unique properties that include the combination of high molecular weight and UV absorption at a high transmittance cutoff up to 430 nm.
In this invention, the polymerizable compound group is attached to the naphthyl ring, for which a formula structure is represented as follows: ##STR2## wherein R.sub.1 is H, Cl, or OCH.sub.3 ; R.sub.2 is a hydroxynaphthyl ring; and R.sub.3 is an unsaturated polymerizable group of a wide selection.
2. Description of the Prior Art
It is known that plastics, inclusive of those used for artificial eye lens implants, are harmed by exposure to solar radiation in the wavelengths of about 290-400 nm. Polymer chains or functional groups in the plastics absorb UV radiation from these wavelengths and the instability of the plastics cause deleterious photochemical reactions.
Photochemical reactions may cause the introduction of functional groups into the polymer; degradation of the polymer chain; or the creation of crosslinkage. To prevent these reactions, a UV absorber is incorporated into the polymer plastic to protect it from the potential degradation of solar radiation.
The ideal absorber should be effective for a substantial period of time, it should not cause discoloration or deterioration of the polymer plastic, and it should not leach out when it comes in contact with a solvent or other low-molecular-weight materials. Also, the peak absorption characteristics of the absorber should ideally be in the most sensitive wavelength to which the polymer is exposed.
It is also important to have a high absorbency index (extinction coefficient) in a UV region and nondestructive emission of the absorbed energy. In addition to the desired photochemical properties, a high absorbency index in wavelengths of from about 290-400 nm with an ideal transmittance cutoff to about 400 nm is needed. UV absorbers can be incorporated into eyeglasses, contact lenses, or intraocular lenses to prevent negative effects caused by UV radiation, such as cataract formation, darkening of the eye's lens, photokeratitis, and erythema. UV radiation up to at least 400 nm should be absorbed to provide protection for the cornea, lens and retina.
Various ophthalmic devices have been developed to absorb UV radiation. Although some of these devices to filter out UV radiation, most of these devices stop wavelengths below 360 nm, but allow radiation between the wavelengths of 360 and430 nm to go through and adversely effect the eye. Furthermore, most of these devices incorporate low-molecular weight compounds that can be leached out of the device through interactions with body fluids and may cause subsequent biotoxicity effects.
U.S. Pat. No. 4,614,709 discloses the use of hydroxyphenyl-based benzotriazole compounds as UV absorbers in silver halide photographic, light-sensitive materials. However, the patent is not directed to or focused on the feasibility of absorption at higher UV ranges and the compounds do not include polymerizable double ring naphthyl derivatives.
U.S. Pat. Nos. 4,380,643 and 4,508,882 disclose the preparation of 2-hydroxyphenyl benzotriazole compounds having a polymerizable unsaturated group on the phenyl ring, which can be homopolymerized or copolymerized with a comonomer to obtain polymeric UV absorbers. These benzotriazole compounds have the formula: ##STR3## where A represents a hydrogen atom, or an acetyl group; R.sup.1 represents a vinyl as shown or haloethyl group or ethyl group; R.sup.2 represents a C.sub.1-4 alkyl group; and n is 1 or 2. R.sub.2.sup.2 need not be the same group in a formula.
U.S. Pat. Nos. 4,380,643 and 4,508,882 disclose that the vinylbenzotriazole compounds provide protection in the 300-330 nm UV range of a stated 290-400 nm solar range. Moreover, a reference to the structural formula in these patents shows that the polymerizable functional group is attached to the benzotriazole portion of the compound.